the amounts you use for each ingredient is totally up to you. I will give you an approximate ratio so it will be well balanced.
12 roma tomatoes, 2 green peppers, 4 jalapeno, 6 garlic and 2 onions seemed to make a nice amount of salsa and the ratio seemed to work out nicely
adjust for how you like your salsa. want it hotter add more jalapeno or leave the seeds and veins in them.
add the sweet and low and a few dashes of the balsamic vinegar
finish it off with a little salt and pepper to taste
Notes
the sweet and low may sound a little odd but even that little amount brings a brightness to the salsa. I would suggest trying it without it and then add it and you will see.